As a key contributing factor to the comfort of air passengers, onboard air conditioning system needs to be tested from time to time in the routine maintenance, especially when complaints arise to its performance by the aircrew, to ensure it works well.
The direct approach to test the performance of onboard air conditioning in the prior art is to acquire the temperature of each key position within the system and then determine its running condition by drawing a reverse Karnaugh map or using a differential method. That being said, temperature measurement is merely an ideal testing method as it requires the mounting of temperature sensors and electric power circuits and/or signal transmission lines at the key positions of onboard air conditioning system. In practicality, however, the tubes for key positions in the onboard air conditioning system are arranged in such complexity that they render the measurement points nearly inaccessible, resulting in a low possibility to obtain an accurate and standard measurement results. Also, the temperature sensors per se require maintaining, which, together with the hardly possible arrangement for a temperature acquisition system, makes the temperature measurement approach fail to receive a widespread application among airline companies.
Such being the case, testing the performance of an onboard air conditioning system conveniently has always been a problem facing the airline industry.